Vertical low pressure chemical vapor deposition (LPCVD) polycrystalline silicon deposition furnace tube equipment and process method for prolonging PM period
By adding ClF3 gas and nitrogen etching process to the vertical LPCVD polycrystalline silicon deposition furnace tube equipment, the problem of short PM cycle was solved, and the equipment was able to operate efficiently and reduce costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-03
- Publication Date
- 2026-04-10
AI Technical Summary
The short PM cycle of existing vertical LPCVD polycrystalline silicon deposition furnace tube equipment leads to frequent equipment maintenance and high costs, and existing improvement methods are either costly or have limited effectiveness.
A ClF3 gas and gas control valve are added to the vertical LPCVD polycrystalline silicon deposition furnace tube equipment. By introducing a combination of ClF3 gas and nitrogen into the reaction chamber, the polycrystalline silicon film on the inner wall surface of the reaction chamber is etched. Combined with nitrogen purging and heating and cooling treatment, the polycrystalline silicon film is removed.
It effectively extended the PM cycle to three times the original length, improved equipment utilization efficiency, reduced equipment maintenance frequency and costs, and maintained the cleanliness of the reaction chamber.
Smart Images
Figure CN121826894A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor technology and relates to a vertical LPCVD polycrystalline silicon deposition furnace tube equipment and a process method for extending the PM cycle. Background Technology
[0002] With the development of integrated circuit and compound semiconductor technology, polycrystalline silicon (POLY) thin films are often used as transistor gate materials due to their excellent semiconductor properties. For example, by doping with phosphorus, polycrystalline silicon thin films can be made into N-type transistors for use as gates of N-type metal-oxide-semiconductor field-effect transistors (NMOS). The threshold voltage of the transistor is adjusted by the concentration of phosphorus doping. Polycrystalline silicon thin films doped with phosphorus or boron are usually called DPOLY.
[0003] In semiconductor manufacturing, DPOLY thin films are typically deposited using a vertical furnace tube system via low-pressure chemical vapor deposition (LPCVD). During deposition, silane (SiH4) and phosphine (PH3) gases are usually introduced, with gas flow rates controlled by mass flow meters (MFC) and valves. The reaction gases are introduced into the reaction chamber through an injector. In addition to the reaction gas path, a nitrogen (N2) path is also provided for purging the reaction chamber and piping after the reaction. The reaction chamber consists of an outer process tube, an inner tube, an insulation tank, and a wafer boat (carrying the wafer). The reaction chamber is located inside the furnace body and is heated by wound resistance wires, with the heating temperature controlled by a TC thermocouple (see schematic diagram). Figure 1 (As shown). During polycrystalline silicon thin film deposition in LPCVD furnace tube equipment, in addition to depositing films on the product wafer, polycrystalline silicon films are also deposited on the surfaces of components such as the inner and outer process tubes, the crystal boat, and the insulation tank, all located within the reaction chamber. With each process cycle, the polycrystalline silicon films deposited on these components become increasingly thick. Once the thickness reaches a certain value, the polycrystalline silicon film gradually peels off, leading to severe particulate contamination. In semiconductor manufacturing processes, particulate contamination can cause varying degrees of open circuits, short circuits, leakage current, and electrical drift in device circuits, even resulting in chip scrap and causing significant economic losses to the company. Analysis of product failure causes revealed that contaminant-related failures account for 60% of all failure factors. Therefore, special attention must be paid to potential contaminants introduced at each stage of the production process.
[0004] Therefore, when the cumulative thickness of the polycrystalline silicon thin film on the surface of each component inside the furnace tube reaches a certain value and the process particle size tends to deteriorate, maintenance of the equipment is required. During maintenance, the LPCVD furnace tube equipment (structural diagram as shown) needs to be cleaned. Figure 1In LPCVD polysilicon deposition, components such as the inner and outer tubes, crystal boat, insulation tank, TC thermocouple, and injection pipe are disassembled for cleaning or replacement to remove the polysilicon film deposited on their surfaces. This process is called "PM" (partial microscopy). The total film thickness accumulated during two PM cycles is called the "PM cycle." PM requires equipment downtime and production stoppage, typically taking 2-3 days from PM to equipment restart. Furthermore, PM necessitates the replacement or cleaning of these components, increasing production costs. Therefore, improving the PM cycle and reducing the frequency of PM is crucial for improving production efficiency and reducing costs.
[0005] For vertical LPCVD polycrystalline silicon furnace tube equipment, the PM cycle of conventional furnace tube equipment, which uses silicon carbide inner tube, silicon carbide boat, quartz injector, quartz insulation barrel, and quartz outer tube, is approximately 10~12um. Figure 2 In a vertical LPCVD polycrystalline silicon furnace, typically 170 wafers are placed on the wafer boat per polycrystalline silicon process. When measuring particle size, three wafers (TOP, Center, Bottom) are selected for measurement. This involves statistically analyzing the particle size changes of polycrystalline silicon thin film after deposition during the production process of existing vertical LPCVD polycrystalline silicon furnace equipment. Figure 2 As shown. Figure 2 The horizontal axis represents the accumulated polysilicon film thickness in the reaction chamber and the wafer measured after each process; the vertical axis represents the number of newly added particles after polysilicon film deposition. It can be seen that the number of newly added particles is typically required to be within 30 during production. After the cumulative thickness reaches 10µm, particle contamination gradually exceeds the limit, requiring PM (particulate matter) treatment. The film structure on the surface of each component inside the reaction chamber and the polysilicon film peeling status before PM treatment are shown below. Figure 3 As shown (where V1 represents components such as the outer tube, inner tube, crystal boat, insulation container, injector, and TC thermocouple; where V2 represents the polycrystalline silicon thin film deposited on the surface of the components, with a thickness of approximately 10 μm; and where V3 represents the localized film peeling phenomenon on the surface of the polycrystalline silicon thin film).
[0006] To extend the PM (partial deposition) cycle, some techniques employ long PM cycle designs to avoid stress on the polycrystalline silicon thin film. These methods include changing component materials, using silicon boats, silicon injectors, and dispersion injectors. However, while optimizing structural design and materials can effectively extend the PM cycle, it also leads to a significant increase in component costs. Furthermore, once the film thickness reaches a certain value, excessive film stress can cause peeling and particulate contamination. Therefore, obtaining a simple, easily modifiable, and significantly extended PM cycle vertical LPCVD polycrystalline silicon equipment, along with a simple, easy-to-operate, and low-cost process for extending the PM cycle of vertical LPCVD polycrystalline silicon deposition furnaces, is crucial for promoting the widespread application of polycrystalline silicon furnaces in semiconductor manufacturing of DPOLY thin films. Summary of the Invention
[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a vertical LPCVD polycrystalline silicon deposition furnace tube equipment with simple structure, easy modification and significant extension of PM cycle, as well as a process method for extending PM cycle that is simple, easy to operate and low in cost.
[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A vertical LPCVD polycrystalline silicon deposition furnace tube device includes a furnace body, an outer tube, and an inner tube. The furnace body, outer tube, and inner tube are nested in sequence to form a reaction chamber. A fifth gas inlet pipe for conveying ClF3 gas and nitrogen gas is connected to the reaction chamber.
[0009] As a further improvement to the above technical solution, the fifth air inlet pipe is also equipped with a gas mass flow meter and a gas control valve.
[0010] As a further improvement to the above technical solution: the outer tube is surrounded by a resistance wire for regulating the temperature inside the reaction chamber.
[0011] As a further improvement to the above technical solution: a thermocouple and a fourth inlet pipe for transmitting nitrogen are provided between the outer pipe and the inner pipe; the outlet of the fourth inlet pipe is located below the outer pipe; a gas mass flow meter and a gas control valve are also provided on the fourth inlet pipe.
[0012] As a further improvement to the above technical solution: the inner tube is also connected to a first inlet pipe, a second inlet pipe and a third inlet pipe for conveying nitrogen; the outlet of the first inlet pipe is located at the bottom of the inner tube and below the fifth inlet pipe; the outlet of the second inlet pipe is located in the middle of the inner tube; and the outlet of the third inlet pipe is located at the top of the inner tube.
[0013] As a further improvement to the above technical solution: the first air inlet pipe, the second air inlet pipe and the third air inlet pipe are all equipped with a gas mass flow meter and a gas control valve.
[0014] As a further improvement to the above technical solution: a liftable support platform is provided below the reaction chamber, and an insulation barrel is provided above the support platform; a crystal boat for loading wafers is provided on the insulation barrel.
[0015] As a further improvement to the above technical solution: the bottom of the reaction chamber is connected to a vacuum pipe via a furnace flange; the other end of the vacuum pipe is connected to a vacuum pump.
[0016] As a general technical concept, the present invention also provides a process method for extending the PM cycle of a vertical LPCVD polysilicon deposition furnace, comprising the following steps: S1. Vertical LPCVD polycrystalline silicon deposition furnace tube equipment for obtaining polycrystalline silicon thin films deposited on the inner wall surface of the reaction chamber; S2. Nitrogen gas is continuously introduced into the reaction chamber of the vertical LPCVD polycrystalline silicon deposition furnace tube equipment as a carrier gas, the vacuum pump is kept on, and ClF3 gas is introduced to etch the polycrystalline silicon thin film deposited on the inner wall surface of the reaction chamber. S3. Stop the ClF3 gas supply, purge the reaction chamber with nitrogen gas, and keep the vacuum pump on. S4. Stop the nitrogen supply and keep the vacuum pump on. S5. Repeat steps S3 and S4 to remove residual ClF3 gas in the reaction chamber.
[0017] As a further improvement to the above technical solution: in step S2, the flow rate of nitrogen is more than three times (including three times) the flow rate of ClF3 gas. As a further improvement to the above technical solution: in step S2, the flow rate of the ClF3 gas is 0.8 slm to 1 slm; the flow rate of the nitrogen gas is 2.5 slm to 3 slm. As a further improvement to the above technical solution: in step S2, the etching is carried out at a temperature of 400℃~500℃; the etching time is 80min~100min; and the pressure in the reaction chamber is controlled to be 100 Pa~120 Pa during the etching process. As a further improvement to the above technical solution: In step S3, the reaction chamber is heated at a heating rate of 5℃ / min for 30min.
[0018] As a further improvement to the above technical solution: in step S4, the reaction chamber is cooled at a rate of 5℃ / min for 30 minutes.
[0019] As a further improvement to the above technical solution: in step S5, steps S3 and S4 are repeated three times to fully remove the polycrystalline silicon thin film suspended on the surface of the reaction chamber through repeated heating and cooling.
[0020] As a further improvement to the above technical solution: In step S2, the following treatment is included before introducing nitrogen gas: S21. Turn on the vacuum pump and check the airtightness of the vertical LPCVD polycrystalline silicon deposition furnace tube equipment to ensure that the vacuum leakage rate in the reaction chamber is <0.2Pa / min; S22. Nitrogen gas is continuously introduced into the reaction chamber of the vertical LPCVD polycrystalline silicon deposition furnace tube equipment for purging, and the vacuum pump is kept on. S23. Stop the nitrogen supply and keep the vacuum pump on. S24. Repeat steps S22 and S23 to remove residual gas and moisture from the reaction chamber and vacuum pipes by repeated purging.
[0021] As a further improvement to the above technical solution: in step S22, the nitrogen gas is introduced for 20 min to 30 min.
[0022] As a further improvement to the above technical solution: in step S23, the vacuum pump is turned on for 20 to 30 minutes.
[0023] As a further improvement to the above technical solution: In step S22, the vertical LPCVD polycrystalline silicon deposition furnace tube equipment includes a furnace body, an outer tube and an inner tube arranged in sequence. The furnace body, the outer tube and the inner tube are arranged in sequence to form a reaction chamber. The reaction chamber is connected to a fifth gas inlet pipe for conveying ClF3 gas and nitrogen gas.
[0024] As a further improvement to the above technical solution, the fifth air inlet pipe is also equipped with a gas mass flow meter and a gas control valve.
[0025] As a further improvement to the above technical solution: the outer tube is surrounded by a resistance wire for regulating the temperature inside the reaction chamber.
[0026] As a further improvement to the above technical solution: a thermocouple and a fourth inlet pipe for transmitting nitrogen are provided between the outer pipe and the inner pipe; the outlet of the fourth inlet pipe is located below the outer pipe; a gas mass flow meter and a gas control valve are also provided on the fourth inlet pipe.
[0027] As a further improvement to the above technical solution: the inner tube is also connected to a first inlet pipe, a second inlet pipe and a third inlet pipe for conveying nitrogen; the outlet of the first inlet pipe is located at the bottom of the inner tube and below the fifth inlet pipe; the outlet of the second inlet pipe is located in the middle of the inner tube; and the outlet of the third inlet pipe is located at the top of the inner tube.
[0028] As a further improvement to the above technical solution: the first air inlet pipe, the second air inlet pipe and the third air inlet pipe are all equipped with a gas mass flow meter and a gas control valve.
[0029] As a further improvement to the above technical solution: a liftable support platform is provided below the reaction chamber, and an insulation barrel is provided above the support platform; a crystal boat for loading wafers is provided on the insulation barrel.
[0030] As a further improvement to the above technical solution: the bottom of the reaction chamber is connected to a vacuum pipe via a furnace flange; the other end of the vacuum pipe is connected to a vacuum pump.
[0031] Compared with the prior art, the advantages of the present invention are as follows: (1) This invention provides a vertical LPCVD polycrystalline silicon deposition furnace tube equipment. By simply adding a ClF3 gas, MFC and valve, the original equipment gas path can be easily modified. Compared with the long PM cycle design, which uses expensive materials and complicated gas path optimization design, it has the advantages of simple structure, easy modification and can greatly extend the PM cycle.
[0032] (2) This invention provides a process method for extending the PM cycle. By periodically introducing ClF3 gas into the reaction chamber of a vertical LPCVD polycrystalline silicon deposition furnace, the polycrystalline silicon thin film on the surface of various components (including inner tube, outer tube, insulation tank, boat, gas inlet pipe, thermocouple, etc.) in the reaction chamber is etched. Under the action of nitrogen, the easily peeled polycrystalline silicon thin film on the inner wall of the reaction chamber is effectively removed, improving the cleanliness of the reaction chamber and extending the PM cycle of the equipment to 3 times the original, thereby improving the efficiency of the equipment. At the same time, this process method is time-saving, requiring only one automatic ClF3 gas etching process, without the need for a lot of time and manpower to disassemble, clean, and reassemble the equipment, resulting in high efficiency and low cost.
[0033] (3) In the process method of the present invention, by optimizing the flow rate and flow ratio of nitrogen and ClF3 gas, on the one hand, nitrogen can be used as a carrier gas, which allows ClF3 gas to diffuse fully to all parts of the reaction chamber, ensuring sufficient etching; on the other hand, nitrogen can be used as a purging gas, which can remove the byproducts generated during etching from the reaction chamber in a timely manner, ultimately improving the etching effect on polycrystalline silicon thin films. In addition, by optimizing the flow rate of ClF3 gas, the polycrystalline silicon thin film on the inner wall surface can be removed quickly while effectively protecting the inner wall of the reaction chamber. This is because an excessively high flow rate will lead to an excessively fast etching rate, which may easily lead to over-etching and damage to the surface, while an excessively low flow rate will lead to insufficient etching. Attached Figure Description
[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.
[0035] Figure 1 This is a schematic diagram of the structure of a conventional vertical LPCVD polycrystalline silicon deposition furnace.
[0036] Figure 2 This is a statistical chart of particulate pollution during the PM cycle for existing conventional vertical LPCVD polycrystalline silicon deposition furnace equipment.
[0037] Figure 3 This is a schematic diagram of the structure of a conventional vertical LPCVD polycrystalline silicon deposition furnace tube during the PM cycle.
[0038] Figure 4 This is a schematic diagram of the vertical LPCVD polycrystalline silicon deposition furnace tube equipment in Embodiment 1 of the present invention.
[0039] Figure 5 This is a statistical chart of particulate pollution during the PM cycle for the vertical LPCVD polycrystalline silicon deposition furnace tube equipment in Embodiment 2 of the present invention.
[0040] Figure 6 The images shown are actual photos of the wafer and insulation tank before and after etching in the vertical LPCVD polycrystalline silicon deposition furnace tube equipment of Embodiment 2 of the present invention. Wherein a represents the wafer before etching, b represents the wafer after etching, c represents the insulation tank before etching, and d represents the insulation tank after etching.
[0041] Legend: 1. Furnace body; 2. Outer tube; 3. Resistance wire; 4. Inner tube; 5. Crystal boat; 6. First air inlet pipe; 7. Second air inlet pipe; 8. Third air inlet pipe; 9. Thermocouple; 10. Fourth air inlet pipe; 11. Insulation tank; 12. Gas mass flow meter; 13. Gas control valve; 14. Support platform; 15. Vacuum pipeline; 16. Furnace mouth flange; 17. Fifth air inlet pipe. Detailed Implementation
[0042] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0043] Example 1 like Figure 4 As shown, the vertical LPCVD polycrystalline silicon equipment of this embodiment includes a furnace body 1, an outer tube 2 and an inner tube 4. The furnace body 1, the outer tube 2 and the inner tube 4 are nested in sequence to form a reaction chamber. A fifth gas inlet pipe 17 for conveying ClF3 gas and nitrogen gas is connected in the reaction chamber.
[0044] In this invention, by adding a fifth inlet pipe 17, ClF3 gas can be transported into the reaction chamber through the fifth inlet pipe 17 (inject5) to etch the polycrystalline silicon thin film on the surface of components such as the outer pipe 2, inner pipe 4, crystal boat 5, insulation barrel 11, first inlet pipe 6 (inject1), second inlet pipe 7 (inject2), third inlet pipe 8 (inject3), and thermocouple 9 in the reaction chamber. During the etching process, ClF3 gas will generate a large number of F free radicals at high temperature. These F free radicals will react violently with the polycrystalline silicon thin film to produce gaseous fluorosilicon compounds. At the same time, under the purging of carrier gas N2, the gaseous fluorosilicon compounds are drawn away by the vacuum pump through the vacuum pipeline, completing the etching and removal process of the polycrystalline silicon thin film. Since the reaction is very intense, it is necessary to control the etching time to retain a layer of polycrystalline silicon thin film on the inner wall, thereby avoiding over-etching and damage to the inner wall of the reaction chamber.
[0045] In this embodiment, the fifth air inlet pipe 17 is also equipped with a gas mass flow meter 12 and a gas control valve 13. Under the combined action of the gas mass flow meter 12 and the gas control valve 13, precise etching of the inner wall surface of the reaction chamber can be achieved, thereby effectively avoiding over-etching and damage to the inner wall of the reaction chamber.
[0046] In this embodiment, the outer tube 2 is surrounded by a resistance wire 3 for regulating the temperature inside the reaction chamber. By connecting the resistance wire 3 to an external power source to heat the reaction chamber, the process can be ensured to be carried out under suitable temperature conditions.
[0047] In this embodiment, a thermocouple 9 and a fourth inlet pipe 10 for transmitting nitrogen are provided between the outer pipe 2 and the inner pipe 4. The thermocouple 9, as a temperature sensor, can be used to monitor the temperature of the reaction chamber and obtain the temperature of the reaction chamber in a timely and accurate manner, facilitating effective control of the reaction chamber temperature. In addition, nitrogen can be delivered into the reaction chamber through the fourth inlet pipe 10 to purge the outer pipe 2 and the inner pipe 4, effectively removing etching products (gaseous fluorosilicon compounds) and helping to extend the PM cycle of the equipment.
[0048] In this embodiment, the outlet of the fourth air inlet pipe 10 (inject4) is located below the outer pipe 2. By optimizing the position of the outlet of the fourth air inlet pipe 10, it is easier to effectively clean the etching products (gaseous fluorosilicon compounds) on the surface of the outer pipe 2 and the inner pipe 4 with nitrogen, and the cleaning efficiency is significantly improved.
[0049] In this embodiment, the fourth air inlet pipe 10 is also equipped with a gas mass flow meter 12 and a gas control valve 13. Under the combined action of the gas mass flow meter 12 and the gas control valve 13, the surface etching products (gaseous fluorosilicone compounds) of the outer pipe 2 and the inner pipe 4 can be accurately cleaned, which can extend the PM cycle of the equipment and reduce the processing cost.
[0050] In this embodiment, the inner tube 4 is also connected to a first inlet pipe 6, a second inlet pipe 7, and a third inlet pipe 8 for conveying nitrogen. In this invention, nitrogen can be conveyed into the inner tube 4 through the first inlet pipe 6, the second inlet pipe 7, and the third inlet pipe 8 to clean the surface of the components inside the inner tube 4, effectively removing etching products (gaseous fluorosilicon compounds), which helps to extend the PM cycle of the equipment.
[0051] In this embodiment, the outlet of the first air inlet pipe 6 is located at the bottom of the inner tube 4 and below the fifth air inlet pipe 17, the outlet of the second air inlet pipe 7 is located in the middle of the inner tube 4, and the outlet of the third air inlet pipe 8 is located at the top of the inner tube 4. By optimizing the positions of the outlets of the first air inlet pipe 6, the second air inlet pipe 7, and the third air inlet pipe 8, it is easier to effectively clean the etching products (gaseous fluorosilicon compounds) on the surface of the components inside the inner tube 4 with nitrogen, and the cleaning efficiency is significantly improved. In this embodiment, the first air inlet pipe 6, the second air inlet pipe 7, and the third air inlet pipe 8 are all equipped with a gas mass flow meter 12 and a gas control valve 13. Under the combined action of the gas mass flow meter 12 and the gas control valve 13, the surface etching products (gaseous fluorosilicone compounds) of the inner pipe 4 can be accurately cleaned, which not only extends the PM cycle of the equipment but also helps to reduce the processing cost.
[0052] In this embodiment, a liftable support platform 14 is provided below the reaction chamber, and an insulation tank 11 is provided above the support platform 14; a wafer boat 5 for loading wafers is provided on the insulation tank 11. In this invention, under the action of the support platform 14, on the one hand, the insulation tank 11 and the wafer boat 5 can be driven to move up and down in the vertical direction to enter and exit the reaction chamber; on the other hand, the wafer can be moved up and down in the inner tube 4 to complete the coating process.
[0053] In this embodiment, the bottom of the reaction chamber is connected to a vacuum pipe 15 via a furnace flange 16; the other end of the vacuum pipe 15 is connected to a vacuum pump.
[0054] In this embodiment, SiH4 and one PH3 line share the first air inlet pipe 6 (inject1), while the other two PH3 lines are connected to the second air inlet pipe 7 (inject2) and the third air inlet pipe 8 (inject3). At the same time, N2 air lines are connected in parallel to both SiH4 and PH3 air lines. The type and flow rate of the gas introduced into the air inlet pipe are controlled by the gas mass flow controller 12 (MFC) and the gas control valve 13, respectively.
[0055] The vertical LPCVD polycrystalline silicon equipment of the present invention can be easily modified by simply adding a ClF3 gas, MFC and valve. Compared with the long PM cycle design, which uses expensive materials and complicated gas path optimization design, it has the advantages of simple structure, easy modification and can significantly extend the PM cycle.
[0056] Example 2 A process method for extending the PM cycle, specifically for extending the PM cycle of a vertical LPCVD polycrystalline silicon deposition furnace, specifically for extending the PM cycle of the vertical LPCVD polycrystalline silicon deposition furnace in Example 1, includes the following steps: Step S1: Set the standby temperature of the reaction chamber to 400℃.
[0057] Step S2: The crystal boat is raised to the process position at a constant speed of 2 mm / s, and during the raising of the crystal boat, 3 slm, 2 slm, 2 slm, and 10 slm of nitrogen are introduced through the first air inlet pipe 6 (inject1), the second air inlet pipe 7 (inject2), the third air inlet pipe 8 (inject3), and the fourth air inlet pipe 10 (inject4), respectively. Step S3: After the crystal boat rises to the process position, set the flow rate of MFC1 / 2 / 3 / 4 / 56 / 7 / 8 / N1 to 0, turn off the nitrogen gas, turn on the vacuum pump, evacuate the reaction chamber to a vacuum using the vacuum pump, and perform a vacuum leak rate test to ensure that the leakage inside the reaction chamber is <0.2Pa / min.
[0058] Step S4: Set the flow rates of MFC2 / 3 / 4 to 3slm, 3slm, and 5slm respectively, and introduce a large amount of nitrogen into the reaction chamber for 30 minutes, while keeping the vacuum pump on.
[0059] Step S5: Set the flow rate of MFC2 / 3 / 4 to 0 slm, turn off the nitrogen gas entering the reaction chamber, and continue to evacuate the reaction chamber for 20 minutes.
[0060] Step S6: Repeat steps S4 and S5 for a total of 3 cycles to ensure that there is no air or moisture residue in the reaction chamber and vacuum pipeline.
[0061] Step S7: Introduce 0.5slm, 0.5slm, and 2slm N2 as carrier gases into the reaction chamber through MFC2, MFC3, and MFC4 respectively, while controlling the pressure in the reaction chamber at 100Pa through the butterfly valve on the vacuum pipeline.
[0062] Step S8: 15m ClF3 gas is introduced into the reaction chamber through MFC-N1 to etch the polycrystalline silicon thin film on the inner wall of the reaction chamber. The etching time is set to 100min. The ClF3 gas will generate a large number of F free radicals at high temperature. These F free radicals will react violently with the polycrystalline silicon thin film to produce gaseous fluorosilicon compounds. At the same time, under the purging of carrier gas N2, the gaseous fluorosilicon compounds are drawn away by the vacuum pump through the vacuum pipeline, completing the etching and removal process of the polycrystalline silicon thin film. Since the reaction is very intense, it is necessary to control the etching time to leave a layer of polycrystalline silicon thin film on the inner wall, thereby avoiding over-etching and damage to the inner wall of the reaction chamber.
[0063] Step S9: Set MFC-N1 to 0slm, turn off ClF3 gas, and stop etching.
[0064] Step S10: Set the flow rates of MFC2 / 3 / 4 to 3slm, 3slm, and 5slm respectively, introduce a large amount of nitrogen into the reaction chamber for 30 minutes, keep the vacuum pump on, set the temperature to 600℃, and the heating rate to 5℃ / min.
[0065] Step S11: Set the flow rate of MFC2 / 3 / 4 to 0 slm, turn off the nitrogen gas entering the reaction chamber, and continue to evacuate the reaction chamber for 30 minutes. Set the temperature to 400℃ and the cooling rate to 5℃ / min.
[0066] Step S12, repeating steps S10 and S11 three times, through cyclic purging and cyclic heating and cooling processes, can completely remove residual ClF3 gas from the reaction chamber and vacuum pipeline.
[0067] Step S11: Set the flow rates of MFC2 / 3 / 4 to 1slm, 1slm, and 1slm respectively, and introduce nitrogen gas into the reaction chamber until the reaction chamber returns to normal pressure.
[0068] Step S12: The etching of the polycrystalline silicon film on the inner wall of the reaction chamber is completed through the above steps. However, since the surface of the polycrystalline silicon film remaining on the inner wall after etching is very rough, it is necessary to cover the inner wall of the reaction chamber with a complete polycrystalline silicon film again. This process is called "Coating". After ClF3 gas etching and Coating, a polycrystalline silicon film with minimal stress, smooth surface and not easy to peel off will be formed on the inner wall of the reaction chamber, thereby improving the cleanliness of the reaction chamber.
[0069] Whenever the cumulative thickness of the polycrystalline silicon film deposited on the surface of the reaction chamber components increases by approximately 8 μm, ClF3 gas is introduced into the reaction chamber according to the above process to etch the easily peeled polycrystalline silicon film. With this improved method, the PM cycle of the vertical LPCVD polycrystalline silicon furnace tube equipment can be extended to 30 μm. The results of the number of newly added particulate contaminants on the surface of the polycrystalline silicon film during the entire PM cycle are as follows: Figure 5 As shown. From Figure 5 As can be seen, particle exceeding the standard only begins to occur when the cumulative thickness reaches approximately 31µm, requiring PM (particulate matter) in the equipment. Simultaneously, combined with... Figure 5 It can be seen that after three etching processes, the cumulative thickness of the film in the reaction chamber reaches about 31 μm, and the polycrystalline silicon process particles gradually exceed the standard, which greatly improves the PM cycle of the LPCVD polycrystalline silicon furnace tube equipment.
[0070] contrast Figure 2 Based on the newly added particles, it can be concluded that when the cumulative polysilicon film thickness in the reaction chamber increases by 8µm, performing ClF3 gas etching on the polysilicon film on the surface of the components in the reaction chamber according to the above process method can effectively reduce the number of newly added particles, extend the PM cycle from the original 10µm to 30µm, significantly reduce the PM frequency of the equipment, and improve the production efficiency of the equipment.
[0071] In addition, by Figure 6 As can be seen, when ClF3 gas is introduced into the reaction chamber of the polycrystalline silicon furnace tube equipment for etching using the above method, the polycrystalline silicon film on the surface of the wafer placed in the reaction chamber is completely etched away, exposing the underlying silicon dioxide film. The wafer surface changes from black (polycrystalline silicon film) to purple (silicon dioxide film). Simultaneously, the polycrystalline silicon film deposited on the surface of the insulation container is also completely etched away, and the surface of the insulation container changes from yellowish-brown and black to white. Therefore, the polycrystalline silicon film on the surfaces of the wafer and the insulation container is effectively removed after processing using the method of this invention.
[0072] Therefore, in this invention, on the one hand, by introducing 1slm of ClF3 gas and 3slm of N2 to etch and remove the polycrystalline silicon thin film in the reaction chamber, the pollution caused by the peeling off of the polycrystalline silicon thin film can be avoided, and the PM cycle of the equipment can be effectively improved. On the other hand, by purging the polycrystalline silicon thin film with nitrogen circulation before etching to ensure that there is no residual air and moisture inside the reaction chamber, and by using a heating and cooling process after etching the polycrystalline silicon thin film to thoroughly purge the residual ClF3 gas, the safety of using ClF3 gas can be guaranteed.
[0073] In addition, the etching effect and particle contamination under different process conditions were tested in this embodiment, as shown in Table 1. Table 1 shows that the insulated container turned white and the wafer turned purple, indicating that the polycrystalline silicon thin film in the reaction chamber was thoroughly etched clean and no particle contamination occurred.
[0074] Table 1. Etching effects and particulate contamination under different process conditions
[0075] The above results demonstrate that this invention provides a process method for extending the PM (partial microcrystalline silicon) etching cycle. By periodically introducing ClF3 gas into the reaction chamber of a vertical LPCVD polycrystalline silicon deposition furnace, and heating the chamber to 400℃~500℃, the polycrystalline silicon thin film on the surface of various components within the reaction chamber (including the inner tube, outer tube, insulation tank, boat, inlet pipe, thermocouples, etc.) is etched. Under the action of nitrogen, the easily peeling polycrystalline silicon thin film on the inner wall of the reaction chamber is effectively removed, improving the cleanliness of the reaction chamber and extending the PM cycle by up to three times, thus increasing the equipment's efficiency. Furthermore, this process is time-efficient, requiring only one automatic ClF3 gas etching process, eliminating the need for extensive time and manpower for disassembly, cleaning, and reassembly of the equipment. It is highly efficient and low-cost.
[0076] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.
Claims
1. A vertical LPCVD polycrystalline silicon deposition furnace tube device, comprising a furnace body (1), an outer tube (2), and an inner tube (4), wherein the furnace body (1), the outer tube (2), and the inner tube (4) are nested sequentially to form a reaction chamber, characterized in that, The reaction chamber is connected to a fifth inlet pipe (17) for conveying ClF3 gas and nitrogen gas.
2. The vertical LPCVD polycrystalline silicon deposition furnace tube equipment according to claim 1, characterized in that, The fifth air inlet pipe (17) is also equipped with a gas mass flow controller (12) and a gas control valve (13).
3. The vertical LPCVD polycrystalline silicon deposition furnace tube equipment according to claim 1 or 2, characterized in that, The outer tube (2) is surrounded by a resistance wire (3) for regulating the temperature inside the reaction chamber. A thermocouple (9) and a fourth inlet pipe (10) for transmitting nitrogen are provided between the outer pipe (2) and the inner pipe (4); the outlet of the fourth inlet pipe (10) is located below the outer pipe (2); a gas mass flow meter (12) and a gas control valve (13) are also provided on the fourth inlet pipe (10). The inner tube (4) is also connected to a first inlet pipe (6), a second inlet pipe (7), and a third inlet pipe (8) for conveying nitrogen; the outlet of the first inlet pipe (6) is located at the bottom of the inner tube (4) and below the fifth inlet pipe (17); the outlet of the second inlet pipe (7) is located in the middle of the inner tube (4); the outlet of the third inlet pipe (8) is located at the top of the inner tube (4); the first inlet pipe (6), the second inlet pipe (7), and the third inlet pipe (8) are all equipped with a gas mass flow meter (12) and a gas control valve (13). Below the reaction chamber is a liftable support platform (14), and above the support platform (14) is a heat preservation barrel (11); on the heat preservation barrel (11) is a crystal boat (5) for loading wafers. The bottom of the reaction chamber is connected to a vacuum pipe (15) via a furnace flange (16); the other end of the vacuum pipe (15) is connected to a vacuum pump.
4. A process method for extending the PM cycle, used to extend the PM cycle of a vertical LPCVD polycrystalline silicon deposition furnace, characterized in that, Includes the following steps: S1. Vertical LPCVD polycrystalline silicon deposition furnace tube equipment for obtaining polycrystalline silicon thin films deposited on the inner wall surface of the reaction chamber; S2. Nitrogen gas is continuously introduced into the reaction chamber of the vertical LPCVD polycrystalline silicon deposition furnace tube equipment as a carrier gas, the vacuum pump is kept on, and ClF3 gas is introduced to etch the polycrystalline silicon thin film deposited on the inner wall surface of the reaction chamber. S3. Stop the ClF3 gas supply, purge the reaction chamber with nitrogen gas, and keep the vacuum pump on. S4. Stop the nitrogen supply and keep the vacuum pump on. S5. Repeat steps S3 and S4 to remove residual ClF3 gas in the reaction chamber.
5. The process method according to claim 4, characterized in that, In step S2, the flow rate of nitrogen is more than three times that of ClF3 gas; the flow rate of ClF3 gas is 0.8 slm to 1 slm; the flow rate of nitrogen is 2.5 slm to 3 slm; the etching is performed at a temperature of 400℃ to 500℃; the etching time is 80 min to 100 min; and the pressure in the reaction chamber is controlled at 100 Pa to 120 Pa during the etching process.
6. The process method according to claim 5, characterized in that, In step S3, the reaction chamber is heated at a rate of 5°C / min for 30 minutes. In step S4, the reaction chamber is cooled at a rate of 5℃ / min for 30 minutes. In step S5, steps S3 and S4 are repeated three times to thoroughly remove the polycrystalline silicon film suspended on the surface of the reaction chamber through repeated heating and cooling.
7. The process method according to any one of claims 4 to 6, characterized in that, In step S2, the following treatment is also included before nitrogen gas is introduced: S21. Turn on the vacuum pump and check the airtightness of the vertical LPCVD polycrystalline silicon deposition furnace tube equipment to ensure that the vacuum leakage rate in the reaction chamber is <0.2Pa / min; S22. Nitrogen gas is continuously introduced into the reaction chamber of the vertical LPCVD polycrystalline silicon deposition furnace tube equipment for purging, and the vacuum pump is kept on. S23. Stop the nitrogen supply and keep the vacuum pump on. S24. Repeat steps S22 and S23 to remove residual gas and moisture from the reaction chamber and vacuum pipes by repeated purging.
8. The process method according to claim 7, characterized in that, In step S22, the nitrogen gas is introduced for 20 min to 30 min. In step S23, the vacuum pump is turned on for 20 to 30 minutes.
9. The process method according to claim 7, characterized in that, In step S22, the vertical LPCVD polycrystalline silicon deposition furnace tube equipment includes a furnace body (1), an outer tube (2) and an inner tube (4) nested in sequence. The furnace body (1), the outer tube (2) and the inner tube (4) are nested in sequence to form a reaction chamber. A fifth gas inlet pipe (17) for conveying ClF3 gas and nitrogen gas is connected in the reaction chamber.
10. The process method according to claim 9, characterized in that, The fifth air inlet pipe (17) is also equipped with a gas mass flow meter (12) and a gas control valve (13). The outer tube (2) is surrounded by a resistance wire (3) for regulating the temperature inside the reaction chamber. A thermocouple (9) and a fourth inlet pipe (10) for transmitting nitrogen are provided between the outer pipe (2) and the inner pipe (4); the outlet of the fourth inlet pipe (10) is located below the outer pipe (2); a gas mass flow meter (12) and a gas control valve (13) are also provided on the fourth inlet pipe (10). The inner tube (4) is also connected to a first inlet pipe (6), a second inlet pipe (7), and a third inlet pipe (8) for conveying nitrogen; the outlet of the first inlet pipe (6) is located at the bottom of the inner tube (4) and below the fifth inlet pipe (17); the outlet of the second inlet pipe (7) is located in the middle of the inner tube (4); the outlet of the third inlet pipe (8) is located at the top of the inner tube (4); the first inlet pipe (6), the second inlet pipe (7), and the third inlet pipe (8) are all equipped with a gas mass flow meter (12) and a gas control valve (13). Below the reaction chamber is a liftable support platform (14), and above the support platform (14) is a heat preservation barrel (11); on the heat preservation barrel (11) is a crystal boat (5) for loading wafers. The bottom of the reaction chamber is connected to a vacuum pipe (15) via a furnace flange (16); the other end of the vacuum pipe (15) is connected to a vacuum pump.